GB2158675A - Obtaining & storing images of geological samples - Google Patents

Description

1 GB 2 158 675 A 1

SPECIFICATION

Process for obtaining images of geological sam ples with a view to their optical analysis and a de vice for its implementation Background of the invention

The invention aims to provide a process ena bling images to be obtained of geological samples with a view to their optical anaylsis, together with 75 a device for its implementation.

These samples, which may be of small dimen sions, appear in the form of cores taken at various depth levels in boreholes. Once brought to the sur face, the cores are prepared for a visual examina- 80 tion, the observations of which form the subject of a descriptive report. This examination report, based on interpretations and codifications using conventional seclimentology symbols and charts, seeks to define, for example, the form, structure, 85 colour and minerological composition of each sample.

The cores are then quickly stored in conditions ensuring their sound preservation, which often lim its the possibilities of direct visual comparison be tween samples made on a given site.

The comparison of these samples and a fortiori the research conducted subsequently, which in volves comparative analyses of samples obtained on different sites, may often only be carried out, for practical reasons, on the single basis of de scriptive reports, in other words on data already interpreted. The analysis work of geologists is con sequently slowed down and rendered more diffi cult.

Summary of the invention

The process according to the invention enables the drawbacks linked to previous interpretation methods to be avoided.

It is characterized in that it includes the sequen tial recording, on a storage or recording medium, of electrical signals translating the images of paral lel lines on the surface of each sample, the images of said lines being successively formed by the rela tive movement of samples in relation to the re cording system. The recorded signals correspond, for example, to images obtained by a selection of at least one spectral band in the radiations re ceived from the said object. The signals obtained are preferably cligitalised whilst being recorded.

The process according to the invention is useful in that the recorded signals can be restored at any moment on an appropriate support, e.g. television screen, photosensitive film or paper, in order to be directly observed or compared with others and, in addition, lend themselves to all sorts of computer aided processings enabling the physical character istics of samples to be deduced objectively without recourse to visual interpretations.

Brief description of the drawings

It will be seen more clearly in the description which follows of the preferred realization modes of the process and its implementation device and by 130 referring to the accompanying drawing on which Figure 1 diagramatically represents the device enabling a geological sample to be moved, where this involves obtaining images, in relation to a re- cording system; Figure 2 represents a realization mode of the recording system where a revolving mirror is used to direct the images of the points of each sample line successively towards a camera, and Figure 3 represents a second realization mode of the recording system where the images of the object are obtained and recorded line by line.

Detailed discussion of the drawings By referring to figure 1, it can be seen that the device includes, for example, a mobile table 1 with dimensions adapted to those of the object 2 to be recorded. When the object is a geological core, the table consists, for example, of a frame several metres long adapted to support the axes of rollers 4 on which a mat 5 is laid. A drive motor 6 of the step-by-step type is used to drive one of the rollers in such a way as it results in a discontinuous displacement of the mat. Above the mobile table a portico 7 is arranged, to which is fixed a box 8 containing an optical and electronic unit for trans forming into recordable signals the images of the object's various parts successively carried into its field by the discontinuous movement of the mat.

This optical and electronic unit includes, for ex ample (Fig.2), an electronic camera 9 and optical means for directing onto the lens of the camera the light successively originating from all the sur face points of the object placed on the table 1.

These means include, for example, a revolving mirror 10 rotated by a motor 11. The mirror rotation axis and the optical axis of the camera are disposed parallel to the displacement direction X'X of the object. In this way, the surface of the object is successively explored following transversal lines parallel to the orthogonal axis Y'Y, the images of the various points of each line being successively recorded by the camera 9. Mirror rotation is controlled in such a way that scanning of the points of each line is carried out in a time interval when the mat 5 is stationary.

This optical and electronic unit may also include (Fig. 3) a camera 9A of a known type suitable for recording the images of surface lines of the object successively formed on its lens. The line images are received by the terminals of adjacent photosensitive sensors. The electrical signals generated by these sensors in response to illumination are successively read, the image of each line corre- sponding to a sequence of signals. The sensors are, for example, of the charge coupled device type (CCD) or made up of photodiodes.

The device also includes a synchronization element 12 connected firstly to a motor 6 by a cable 13 and secondly to the optical and electronic unit contained in the box 8 by a cable 14. The synchronization element 12 is provided with an internal clock and a counter and, in response to the pulses produced by the clock, it generates successive control signals which are applied to the motor 6. The 2 GB 2 158 675 A 2 latter then turns from an angular increment which has the effect of displacing the mat and putting a new surface line of the object inside the field of the camera 9 or 9A. The progression step is deter mined according to the definition chosen for the image. A linear resolution is preferably chosen in the order of 0.5 mm at the most by placing it in the field of an optical and electronic unit having an an gular resolution close to 0.5 mrad at a distance of about 1 m. The mat 5 having progressed by one step, the synchronization element then generates from the clock signals a command signal for re cording of the image by the recording system.

Where the combination of an electronic camera and revolving mirror (Fig. 2) is used, the command 80 signal is adapted to synchronize the rotation speed of the motor 11 and to trigger off acquisition of the image and its transformation into electrical signals.

In the case of a camera used for recording by lines (Fig. 3), the command signal is adapted to trigger 85 off the sequential reading of the various sensors of the sensitive terminal. In all cases, the indications of the counter with each progression step of the mat are transferred onto the corresponding record ing which enables the image of any surface position of the object to be quickly retrieved.

On can also arrange all along the object and on its sides a centimetric scale enabling a determined area of the surface to be found very quickly.

The electrical signals derived from the optical and electronic unit are transmitted by a cable 15 to a microcomputer 16 which converts them into nu meric words then transferred to a recording device 17, for example a tape recorder. The signals can also be transferred to a display device such as a 100 TV monitor in such a way as to obtain a direct or different representation of the surface of the re corded object.

The microcomputer is also connected to a panel 19 enabling an operator to launch recording opera tions or to control special operations processing recorded data. The microcomputer is programmed, for example, to carry out processing in real time of data supplied by the camera before being recorded on the recording device 17, or in delayed time as regards pre-recorded data.

The camera can be connected to an optical filter ing device allowing for selection of one or several bands over the whole width of the frequency spec trum of the radiation received from the object, from ultraviolet to micro-waves (wave lengths be tween 30nm and 30cm). The visible spectral band enables sedimentary figures to be identified by the quantification of colours and their geometrical ar rangement: lineaments, deformations, etc. The spectral band situated in the thermal infrared ena bles sedimentary groups to be differentiated ac cording to their thermal inertia. The ultrahigh frequencies enable information to be obtained con cerning the fluid content of constituents and their granulometry or roughness.

The process according to the invention, when applied to the acquisition of images of geological cores, can be favourably implemented on the same extraction sites, on land, on a ship or on an off- shore drilling platform. The cores, which have just been calliphered and prepared by truncating and sawing following their axis, are arranged on the mobile table 1 prior to recording operations being carried out.

The process, even when the samples are no longer readily available for examination, enables a subsequent reproduction to be made of the images recorded for visual comparisons and consequently eliminates the need for the written codified descriptions previously required.

The process according to the invention is particularly useful in that it enables all sorts of systematic numeric processings to be made of recorded data. The elements can be classified according to their colours by referring to stored charts and, after simplification of the image by reduction to its contours, specialized pattern detection programmes can be applied for identifying its components. The localization of discontinuities between layers enables calculation to be made of the spatial frequency of alternations and quantification of rhythms and sedimentary sequences. By means of a suitable programming applying known processes for calculating derivatives, the linear parts of each image can be isolated and it then becomes possible to distinguish the overriding strata fracturing directions.

The computer-aided processing steps mentioned above are, for example, already used for the treatment of images taken from a plane or satellite.

These numeric processings can be applied to cores calliphered at spaced out intervals or from different sites. The large amount of data which can be obtained by these means and their objective character facilitates correlation of samplings.

Claims (13)

1. Process for obtaining images of geological samples with a view to their optical analysis, char acterized in that it includes the sequential record ing, on a recording medium, of electrical signals translating the images of surface parallel lines of each sample, the images of these lines being successively formed by relative displacement of each sample in relation to the recording system.

2. Process according to claim 1, characterized in that the images translated by the signals recorded are obtained by a selection of at least one spectral band in the radiation of each sample.

3. Process according to claim 1, characterized in that it includes the digitilization of signals whilst they are being recorded. 120

4. Acquisition device for implementing the process according to claim 1, characterized in that it comprises a recording system, means for moving each geological sample in relation to the recording system which includes optical means for successively forming the images of parallel lines of the said sample, means for translating the images of each line into a sequence of signals and means for storing (17) said signals.

5. Acquisition device according to claim 4, char- acterized in that the optical means include a re- 3 GB 2 158 675 A 3 flecting mobile element (10) for successively directing, by scanning, the images of all the points of each line onto an electronic camera (9).

6. Acquisition device according to claim 4, char- acterized in that the means for translating the images of each line into a sequence of signals comprising a transducer made up of a multiplicity of aligned photosensitive elements, the responses of which are read successively.

7. Acquisition device according to claim 4, characterized in that the means for translating the images of each line into a sequence of signals include a charge-coupled device.

8. Acquisition device according to one of claims 5 to 7, characterized in that it includes an electronic unit (16) for digitalization of said signals.

9. Acquisition device according to claim 4, characterized in that it includes optical filtering means for selecting at least one electromagnetic spectal band received from said samples.

10. Acquisition device according to one of claims 5 to 7, characterized in that it includes an electronic unit (16) for digitalizing said signals and for processing the digitalized signals.

11. Acquisition device according to claim 4, characterized in that the means for moving each geological sample consist of a mobile table (1), a step-by-step drive motor (6) for the mobile table and in that it includes synchronization means (12) for alternately controlling the drive motor and the recording system.

12. A process as claimed in claim 1, and substantially as hereinbefore described.

13. A device as claimed in Claim 4, and sub- stantially as hereinbefore described with reference to the accompanying drawings.

Printed in the UK for HMSO, D8818935, 9,85, 7102. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.